Message-ID: <VI1PR04MB5807E840A7A5AF3D65E663CFF2FB0@VI1PR04MB5807.eurprd04.prod.outlook.com>
Date:   Tue, 24 Nov 2020 16:11:58 +0000
From:   Camelia Alexandra Groza <camelia.groza@....com>
To:     Maciej Fijalkowski <maciej.fijalkowski@...el.com>
CC:     "kuba@...nel.org" <kuba@...nel.org>,
        "brouer@...hat.com" <brouer@...hat.com>,
        "saeed@...nel.org" <saeed@...nel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "Madalin Bucur (OSS)" <madalin.bucur@....nxp.com>,
        Ioana Ciornei <ioana.ciornei@....com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH net-next v4 2/7] dpaa_eth: add basic XDP support

> -----Original Message-----
> From: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
> Sent: Tuesday, November 24, 2020 15:51
> To: Camelia Alexandra Groza <camelia.groza@....com>
> Cc: kuba@...nel.org; brouer@...hat.com; saeed@...nel.org;
> davem@...emloft.net; Madalin Bucur (OSS)
> <madalin.bucur@....nxp.com>; Ioana Ciornei <ioana.ciornei@....com>;
> netdev@...r.kernel.org
> Subject: Re: [PATCH net-next v4 2/7] dpaa_eth: add basic XDP support
> 
> On Mon, Nov 23, 2020 at 07:36:20PM +0200, Camelia Groza wrote:
> > Implement the XDP_DROP and XDP_PASS actions.
> >
> > Avoid draining and reconfiguring the buffer pool at each XDP
> > setup/teardown by increasing the frame headroom and reserving
> > XDP_PACKET_HEADROOM bytes from the start. Since we always reserve
> an
> > entire page per buffer, this change only impacts Jumbo frame scenarios
> > where the maximum linear frame size is reduced by 256 bytes. Multi
> > buffer Scatter/Gather frames are now used instead in these scenarios.
> >
> > Allow XDP programs to access the entire buffer.
> >
> > The data in the received frame's headroom can be overwritten by the XDP
> > program. Extract the relevant fields from the headroom while they are
> > still available, before running the XDP program.
> >
> > Since the headroom might be resized before the frame is passed up to the
> > stack, remove the check for a fixed headroom value when building an skb.
> >
> > Allow the meta data to be updated and pass the information up the stack.
> >
> > Scatter/Gather frames are dropped when XDP is enabled.
> >
> > Acked-by: Madalin Bucur <madalin.bucur@....nxp.com>
> > Signed-off-by: Camelia Groza <camelia.groza@....com>
> > ---
> > Changes in v2:
> > - warn only once if extracting the timestamp from a received frame fails
> >
> > Changes in v3:
> > - drop received S/G frames when XDP is enabled
> >
> > Changes in v4:
> > - report a warning if the MTU is too hight for running XDP
> > - report an error if opening the device fails in the XDP setup
> >
> >  drivers/net/ethernet/freescale/dpaa/dpaa_eth.c | 166
> ++++++++++++++++++++++---
> >  drivers/net/ethernet/freescale/dpaa/dpaa_eth.h |   2 +
> >  2 files changed, 152 insertions(+), 16 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> > index 88533a2..8acce62 100644
> > --- a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> > +++ b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
> > @@ -53,6 +53,8 @@
> >  #include <linux/dma-mapping.h>
> >  #include <linux/sort.h>
> >  #include <linux/phy_fixed.h>
> > +#include <linux/bpf.h>
> > +#include <linux/bpf_trace.h>
> >  #include <soc/fsl/bman.h>
> >  #include <soc/fsl/qman.h>
> >  #include "fman.h"
> > @@ -177,7 +179,7 @@
> >  #define DPAA_HWA_SIZE (DPAA_PARSE_RESULTS_SIZE +
> DPAA_TIME_STAMP_SIZE \
> >  		       + DPAA_HASH_RESULTS_SIZE)
> >  #define DPAA_RX_PRIV_DATA_DEFAULT_SIZE
> (DPAA_TX_PRIV_DATA_SIZE + \
> > -					dpaa_rx_extra_headroom)
> > +					XDP_PACKET_HEADROOM -
> DPAA_HWA_SIZE)
> >  #ifdef CONFIG_DPAA_ERRATUM_A050385
> >  #define DPAA_RX_PRIV_DATA_A050385_SIZE (DPAA_A050385_ALIGN -
> DPAA_HWA_SIZE)
> >  #define DPAA_RX_PRIV_DATA_SIZE (fman_has_errata_a050385() ? \
> > @@ -1733,7 +1735,6 @@ static struct sk_buff *contig_fd_to_skb(const
> struct dpaa_priv *priv,
> >  			SKB_DATA_ALIGN(sizeof(struct skb_shared_info)));
> >  	if (WARN_ONCE(!skb, "Build skb failure on Rx\n"))
> >  		goto free_buffer;
> > -	WARN_ON(fd_off != priv->rx_headroom);
> >  	skb_reserve(skb, fd_off);
> >  	skb_put(skb, qm_fd_get_length(fd));
> >
> > @@ -2349,12 +2350,62 @@ static enum qman_cb_dqrr_result
> rx_error_dqrr(struct qman_portal *portal,
> >  	return qman_cb_dqrr_consume;
> >  }
> >
> > +static u32 dpaa_run_xdp(struct dpaa_priv *priv, struct qm_fd *fd, void
> *vaddr,
> > +			unsigned int *xdp_meta_len)
> > +{
> > +	ssize_t fd_off = qm_fd_get_offset(fd);
> > +	struct bpf_prog *xdp_prog;
> > +	struct xdp_buff xdp;
> > +	u32 xdp_act;
> > +
> > +	rcu_read_lock();
> > +
> > +	xdp_prog = READ_ONCE(priv->xdp_prog);
> > +	if (!xdp_prog) {
> > +		rcu_read_unlock();
> > +		return XDP_PASS;
> > +	}
> > +
> > +	xdp.data = vaddr + fd_off;
> > +	xdp.data_meta = xdp.data;
> > +	xdp.data_hard_start = xdp.data - XDP_PACKET_HEADROOM;
> > +	xdp.data_end = xdp.data + qm_fd_get_length(fd);
> > +	xdp.frame_sz = DPAA_BP_RAW_SIZE;
> > +
> > +	xdp_act = bpf_prog_run_xdp(xdp_prog, &xdp);
> > +
> > +	/* Update the length and the offset of the FD */
> > +	qm_fd_set_contig(fd, xdp.data - vaddr, xdp.data_end - xdp.data);
> 
> Shouldn't you do this update based on xdp.data_meta, not xdp.data?

Both the xdp.data_meta and xdp.data can be updated when the XDP program runs.

In case of XDP_PASS, when building an skb around an fd, we need to know where the data starts for calling skb_reserve(). The metadata set by the XDP program is part of the skb's headroom, not part of the packet data. So we adjust the fd's offset and length based on the data, not the metadata. We let the skb know it has metadata set in its headroom through skb_metadata_set().

For XDP_TX we don't pass metadata to the hardware, and for XDP_REDIRECT the xdp_frame points to this information, so there is no need for keeping track of it in the fd.

> > +
> > +	switch (xdp_act) {
> > +	case XDP_PASS:
> > +		*xdp_meta_len = xdp.data - xdp.data_meta;
> > +		break;
> > +	default:
> > +		bpf_warn_invalid_xdp_action(xdp_act);
> > +		fallthrough;
> > +	case XDP_ABORTED:
> > +		trace_xdp_exception(priv->net_dev, xdp_prog, xdp_act);
> > +		fallthrough;
> > +	case XDP_DROP:
> > +		/* Free the buffer */
> > +		free_pages((unsigned long)vaddr, 0);
> > +		break;
> > +	}
> > +
> > +	rcu_read_unlock();
> > +
> > +	return xdp_act;
> > +}
> > +
> >  static enum qman_cb_dqrr_result rx_default_dqrr(struct qman_portal
> *portal,
> >  						struct qman_fq *fq,
> >  						const struct qm_dqrr_entry
> *dq,
> >  						bool sched_napi)
> >  {
> > +	bool ts_valid = false, hash_valid = false;
> >  	struct skb_shared_hwtstamps *shhwtstamps;
> > +	unsigned int skb_len, xdp_meta_len = 0;
> >  	struct rtnl_link_stats64 *percpu_stats;
> >  	struct dpaa_percpu_priv *percpu_priv;
> >  	const struct qm_fd *fd = &dq->fd;
> > @@ -2362,12 +2413,14 @@ static enum qman_cb_dqrr_result
> rx_default_dqrr(struct qman_portal *portal,
> >  	enum qm_fd_format fd_format;
> >  	struct net_device *net_dev;
> >  	u32 fd_status, hash_offset;
> > +	struct qm_sg_entry *sgt;
> >  	struct dpaa_bp *dpaa_bp;
> >  	struct dpaa_priv *priv;
> > -	unsigned int skb_len;
> >  	struct sk_buff *skb;
> >  	int *count_ptr;
> > +	u32 xdp_act;
> >  	void *vaddr;
> > +	u32 hash;
> >  	u64 ns;
> >
> >  	fd_status = be32_to_cpu(fd->status);
> > @@ -2423,35 +2476,67 @@ static enum qman_cb_dqrr_result
> rx_default_dqrr(struct qman_portal *portal,
> >  	count_ptr = this_cpu_ptr(dpaa_bp->percpu_count);
> >  	(*count_ptr)--;
> >
> > -	if (likely(fd_format == qm_fd_contig))
> > +	/* Extract the timestamp stored in the headroom before running
> XDP */
> > +	if (priv->rx_tstamp) {
> > +		if (!fman_port_get_tstamp(priv->mac_dev->port[RX], vaddr,
> &ns))
> > +			ts_valid = true;
> > +		else
> > +			WARN_ONCE(1, "fman_port_get_tstamp failed!\n");
> > +	}
> > +
> > +	/* Extract the hash stored in the headroom before running XDP */
> > +	if (net_dev->features & NETIF_F_RXHASH && priv->keygen_in_use
> &&
> > +	    !fman_port_get_hash_result_offset(priv->mac_dev->port[RX],
> > +					      &hash_offset)) {
> > +		hash = be32_to_cpu(*(u32 *)(vaddr + hash_offset));
> > +		hash_valid = true;
> > +	}
> > +
> > +	if (likely(fd_format == qm_fd_contig)) {
> > +		xdp_act = dpaa_run_xdp(priv, (struct qm_fd *)fd, vaddr,
> > +				       &xdp_meta_len);
> > +		if (xdp_act != XDP_PASS) {
> > +			percpu_stats->rx_packets++;
> > +			percpu_stats->rx_bytes += qm_fd_get_length(fd);
> > +			return qman_cb_dqrr_consume;
> > +		}
> >  		skb = contig_fd_to_skb(priv, fd);
> > -	else
> > +	} else {
> > +		/* XDP doesn't support S/G frames. Return the fragments to
> the
> > +		 * buffer pool and release the SGT.
> > +		 */
> > +		if (READ_ONCE(priv->xdp_prog)) {
> > +			WARN_ONCE(1, "S/G frames not supported under
> XDP\n");
> > +			sgt = vaddr + qm_fd_get_offset(fd);
> > +			dpaa_release_sgt_members(sgt);
> > +			free_pages((unsigned long)vaddr, 0);
> > +			return qman_cb_dqrr_consume;
> > +		}
> >  		skb = sg_fd_to_skb(priv, fd);
> > +	}
> >  	if (!skb)
> >  		return qman_cb_dqrr_consume;
> >
> > -	if (priv->rx_tstamp) {
> > +	if (xdp_meta_len)
> > +		skb_metadata_set(skb, xdp_meta_len);
> > +
> > +	/* Set the previously extracted timestamp */
> > +	if (ts_valid) {
> >  		shhwtstamps = skb_hwtstamps(skb);
> >  		memset(shhwtstamps, 0, sizeof(*shhwtstamps));
> > -
> > -		if (!fman_port_get_tstamp(priv->mac_dev->port[RX], vaddr,
> &ns))
> > -			shhwtstamps->hwtstamp = ns_to_ktime(ns);
> > -		else
> > -			dev_warn(net_dev->dev.parent,
> "fman_port_get_tstamp failed!\n");
> > +		shhwtstamps->hwtstamp = ns_to_ktime(ns);
> >  	}
> >
> >  	skb->protocol = eth_type_trans(skb, net_dev);
> >
> > -	if (net_dev->features & NETIF_F_RXHASH && priv->keygen_in_use
> &&
> > -	    !fman_port_get_hash_result_offset(priv->mac_dev->port[RX],
> > -					      &hash_offset)) {
> > +	/* Set the previously extracted hash */
> > +	if (hash_valid) {
> >  		enum pkt_hash_types type;
> >
> >  		/* if L4 exists, it was used in the hash generation */
> >  		type = be32_to_cpu(fd->status) & FM_FD_STAT_L4CV ?
> >  			PKT_HASH_TYPE_L4 : PKT_HASH_TYPE_L3;
> > -		skb_set_hash(skb, be32_to_cpu(*(u32 *)(vaddr +
> hash_offset)),
> > -			     type);
> > +		skb_set_hash(skb, hash, type);
> >  	}
> >
> >  	skb_len = skb->len;
> > @@ -2671,6 +2756,54 @@ static int dpaa_eth_stop(struct net_device
> *net_dev)
> >  	return err;
> >  }
> >
> > +static int dpaa_setup_xdp(struct net_device *net_dev, struct bpf_prog
> *prog)
> > +{
> > +	struct dpaa_priv *priv = netdev_priv(net_dev);
> > +	struct bpf_prog *old_prog;
> > +	int err, max_contig_data;
> > +	bool up;
> > +
> > +	max_contig_data = priv->dpaa_bp->size - priv->rx_headroom;
> > +
> > +	/* S/G fragments are not supported in XDP-mode */
> > +	if (prog &&
> > +	    (net_dev->mtu + VLAN_ETH_HLEN + ETH_FCS_LEN >
> max_contig_data)) {
> > +		dev_warn(net_dev->dev.parent,
> > +			 "The maximum MTU for XDP is %d\n",
> > +			 max_contig_data - VLAN_ETH_HLEN -
> ETH_FCS_LEN);
> > +		return -EINVAL;
> > +	}
> > +
> > +	up = netif_running(net_dev);
> > +
> > +	if (up)
> > +		dpaa_eth_stop(net_dev);
> > +
> > +	old_prog = xchg(&priv->xdp_prog, prog);
> > +	if (old_prog)
> > +		bpf_prog_put(old_prog);
> > +
> > +	if (up) {
> > +		err = dpaa_open(net_dev);
> > +		if (err) {
> > +			dev_err(net_dev->dev.parent, "dpaa_open()
> failed\n");
> > +			return err;
> 
> So you decided not to take advantage of extack messages?

Sorry, I put more emphasis on reporting the messages than on the actual means to do it. I'll wait, if you have more comments, and respin.

> > +		}
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static int dpaa_xdp(struct net_device *net_dev, struct netdev_bpf *xdp)
> > +{
> > +	switch (xdp->command) {
> > +	case XDP_SETUP_PROG:
> > +		return dpaa_setup_xdp(net_dev, xdp->prog);
> > +	default:
> > +		return -EINVAL;
> > +	}
> > +}
> > +
> >  static int dpaa_ts_ioctl(struct net_device *dev, struct ifreq *rq, int cmd)
> >  {
> >  	struct dpaa_priv *priv = netdev_priv(dev);
> > @@ -2737,6 +2870,7 @@ static int dpaa_ioctl(struct net_device *net_dev,
> struct ifreq *rq, int cmd)
> >  	.ndo_set_rx_mode = dpaa_set_rx_mode,
> >  	.ndo_do_ioctl = dpaa_ioctl,
> >  	.ndo_setup_tc = dpaa_setup_tc,
> > +	.ndo_bpf = dpaa_xdp,
> >  };
> >
> >  static int dpaa_napi_add(struct net_device *net_dev)
> > diff --git a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.h
> b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.h
> > index da30e5d..94e8613 100644
> > --- a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.h
> > +++ b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.h
> > @@ -196,6 +196,8 @@ struct dpaa_priv {
> >
> >  	bool tx_tstamp; /* Tx timestamping enabled */
> >  	bool rx_tstamp; /* Rx timestamping enabled */
> > +
> > +	struct bpf_prog *xdp_prog;
> >  };
> >
> >  /* from dpaa_ethtool.c */
> > --
> > 1.9.1
> >

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